Refrigerating system



June 22, 1937. E. R. GILL, SR 2,084,730

REFRIGERATING SYSTEM Original Filed May 7, 1930 2 Sheets-Sheet 1INVENTOR ATTORNEYS 1930 2 Sheets-Sheet 2 June 22, 1937. E. R. GILL. SR

REFRIGERATING SYSTEM Original Filed May '7 Patented June 22, 1937 UNITEDSTATES PATENT OFFICE REFRIGERATING SYSTEM Application May '7, 1930,Serial No. 450,451 Renewed August 18, 1936 29 Claims.

My invention relates to refrigerating systems of the type employing avolatile refrigerant which at the higher range of temperature is a gasor vapor and at the lower range a liquid, for example, sulphur dioxide,and includes as equivalents refrigerants of the ammonia type.

In systems of the above type or typesthe reirigerant is converted toliquid phase and introduced into a vessel generally known as anevaporator which is in heat exchange relation with a body to berefrigerated. Here the refrigerant is permitted to vaporize, the gas orvapor being periodically conveyed away from the vaporizing region andrecondensed. Such a process is generally cyclic, and as ordinarilypracticed in house hold apparatus is discontinuous, in that theliquefaction step is brought about automatically by a suitableheat-responsive control whenever the temperatureof the refrigeratedregion rises to a given point, for example 28 F. The compressor,

if the system be of the compressor type, is thereupon set into operationby an electric motor to draw the vapor from the region of refrigerationand condense it to a liquid, thereby causing a lowering of thetemperature of such region. This step of the cycle continues until thetemperature has been lowered to a predetermined degree, for example, 8F. whereupon the motor circuit is opened and the compressor stops.

30 The temperature and pressure of the refrigerant then gradually riseuntil the temperature is at the figure previously mentioned, viz, 28 F.,whereupon another cycle of operation is initiated as before described.

As heretofore practiced, such cycles automatically succeed each otherwithout any attention on the part of the user. However, on account ofthe presence of moisture in the refrigerated region, a deposit of ice orfrost gradually accumu- 4O lates upon the evaporator or cooling pipeswhich increases in thickness until the eificiency of the system isseriously impaired and it then becomes necessary to defrost the pipes.

This is ordinarily accomplished by the use of a hand operated switch orother device which prevents the closing of the motor circuit, so thatcompression does not begin until the temperature of the refrigeratedregion has risen sufficiently above 32 F. to cause a melting of thefrost on the pipes. The hand device is then shifted to permit theresumption of the cycles heretofore described.

It has also been proposed to make use of devices which may be set byhand for varying the normal cycle by preventing the closing of the motorcircuit until the temperature of the refrigerated region has risensufficiently to cause defrosting, and after such cycle the part so setby hand is automatically restored to initial position so that the normalcycles follow each other until the hand device is again operated.

In all of the above systems defrosting is accomplished only when somedevice is moved or operated by the user. In case the user does not payproper attention to the apparatus so as to cause defrosting of thecooling pipes, the system becomes inefficient by reason of the heatinsulating effect of the frost on the pipes, the compressor must bedriven more than would be necessary with defrosted pipes, andunnecessary expense results.

In accordance with another system the upper limit of temperature of eachcycle is sufliciently high to cause defrosting during each cycle. Thedisadvantage of such system is ineificiency due to the fact that thecompressor, after being started at the high temperature must be operatedfor a much longer time than when started at a lower temperature in orderto bring the refrigerated region to the desired low temperature whichconstitutes the lower limit.

It has also been proposed to automatically defrost by a device which isunitary with the normal control. is impractical because the defrostingmechanism is in no sense separate and cannot be adapted to varyingconditions.

It has also been proposed to defrost an evaporator by periodicallyheating it by an electric heater. This system is not practical and isdisadvantageous on account of the electrical equipment in thecompartment to be refrigerated and the heat thereby introduced.

According to my invention, defrosting is accomplished by automaticallyvarying cycles from normal or introducing certain modifications ofcontrol whereby the temperature of the evaporator automatically risesabove the normal operating range and to above frosting temperature atcertain times. This is accomplished in the preferred form by imposing anadditional resistance on the pressure-responsive member of the energysupply control means at recurring intervals between a plurality ofnormal cycles or at given intervals. Preferably, a counting device isused which is actuated by cyclic movement of the energy supply means tocount cycles, after a given number of which the additional resistance isimposed.

My invention will become clear by reference to The particularconstruction I refer to the following specification taken in conjunctionwith the accompanying drawings, forming part of this specification.

Among the objects of my invention are: To provide a practical fullyautomatic defrosting mechanism; to provide a defrosting mechanism whichis adaptable to varying conditions; to provide a fully automaticdefrosting mechanism which may be separately adjusted with respect tothe normal control apparatus and which may be rendered ineffective forcertain purposes.

My invention is capable of many variations, some of which areillustrated in the accompanying drawings, of which Fig. 1 is adiagrammatic view of a refrigerating invention.

Fig. 4 is a section on line 4-4 of Fig. 2.

The system of Fig. l is well known and comprises an electric motor a foroperating a compressor b, for compressing a volatile refrigerant, forexample sulphur dioxide. A pipe 0 connects the high pressure side of thecompressor with the condenser d where it is liquefied. The liquid isforced through pipe e to the valve 1 for controlling escape of liquid tothe low pressure side of the system, after which the refrigerant ispermitted to enter the cooling pipes or units 9 in the region which isto be refrigerated. Evaporation of the refrigerant takes place and thevapor is drawn through pipe h to the low pressure side of the compressorD to complete the cycle.

A pipe i2 connects pipe h with the metal bellows ll of the switch It forclosing and opening the power circuit of the electric motor a andthereby starting and stopping the motor and the compressor.

One form of defrosting regulator is shown in Figs. 2 and 3. Thisregulator is here combined with a well known type of electric switch forcon trolling the closing and opening of the power circuit of theelectric motor which drives the compressor.

The switch shown comprises a base or body it), upon which is mounted ametal bellows l I, the ends of which are closed except for the pipe l2which is connected to the low pressure side of the system. A spider l3comprising an apertured top plate and depending arms i4 is secured tothe base and limits the expansion of the bellows.

The nain switch arm I5 is clamped by lock nuts I6 against the shoulderformed by an enlarged part of the pivot pin I! which is journaled inears I8 integral with the spider I3. The free end of the switch arm I5is provided with a horizontal pin [9 upon which are journaled a pair ofarms 20. These arms are united at one end by a hardened metal wear block2| and rivets 22 and intermediate their ends by rivet 23. The other endsof said arms are spread to receive an insulator 24 which turns freely ona rod 25 fixed to the arms.

The switch also comprises contacts 6 and 21. The contact 26 is fixed tothe free end of a flat spring 28 which is secured to the body. Thecontact 21 is fixed to the free end of a flat spring 29 which is securedby rivet 30 to a plate 3i. The plate 3| is provided with integral ears32 which carry a pivot pin 33 upon which the insulator 24 is looselymounted. The plate 3| also Las depending lugs 3 which are Journaled on apin 90* fixed to the body.

A roller 34 is mounted on a pin 35 which is Journaled in the upper endsof side plates 35 of a support 31. The lower ends of the side plates arerotatable on a pin 38 and the latter is rigidly mounted in the standards39 which are secured to the base by rivets 40. A coil spring 4isurrounds the pin 38, one end bearing against the rod 42 and the otheragainst the support 31, whereby the roller 34 is urged toward the left,Fig. 3, and against the wear block 2|.

The switch arm 15 is connected by pivot pin 43 with a stud 44 which isfixed to the upper wall 45 of the metal bellows H.

The parts hereinbeiore mentioned operate briefly as follows: Assumingthe switch to be in open circuit position, the compressor is not workingand the pressure on the low pressure side 01'. the system is rising.When the temperature of the region surrounding the cooling units risesto approidmately 28 F. the pressure of the refrigerant causes thebellows II to expand sufiiciently to raise the arm l5 into the positionof Fig. 3, the roller 34 pressing strongly against the wear block 2| andclosing the switch, whereupon the electric motor is started and thecompressor operated thereby.

By varying the resistance of the arm I! to upward movement, the degreeof temperature at which the switch closes the motor circuit can beeither raised or lowered. This is ordinarily accomplished by adjustmentsprings as shown. The circuit closing temperature may be raised byincreasing the resistance to compression of the spring 46 whichsurrounds the rod 41 and bears against the base and a nut (not shown)threaded thereon. The rod passes through an opening in the base and ispivoted at 48 to the arm I5.

This means provides for the closing of the circuit under ordinaryrunning conditions, as when the temperature is to be allowed to rise ashigh as 28 F. In case it is desired to lower this limit for the purposeof running at a lower average temperature such result may beaccomplished by the following means.

A plate 49 having a standard 50 is secured to the body. The standard isprovided with a bearing 5| within which is journaled a shaft 52. Anoperating arm 53 is rigid with the outer end of said shaft and carriesat its free end a sleeve 54 and sliding detent or bolt 55 which isadapted to engage any one of a series of holes 56 formed in andextending through the standard 50 and dial plate 51. The knurled knob 58is rigid with the bolt 55 and the same are normally held in the positionshown by a spring within the sleeve 54.

Upon the inner end of the shaft 52 is a coil spring 59, one end of whichis pinned through the shaft and the other extends outward therefrom asshown in Fig. 2. When the bolt 55 is in the hole I of the dial, whichprovides for ordinary or average running conditions, the spring 59 isinactive. Upon moving the arm 53 in a counterclockwise direction to oneof the holes 3 to 6 inclusive of the dial the free end of the spring 59is caused to press against the lower surface of the shaft I9 with apressure which increases as the arm moves toward the hole 8.

Such pressure upon the shaft l9 aids the bellows in elevating the switcharm l5 to close the motor circuit, and consequently lowers the upperlimit or range of the working temperature of the system, each hole from3 to 5 providing for a definite and progressively lower temperature, thevalues of which may be definitely regulated within certain limits bymeans of a spring pressed pin 66, which yieldingly opposes the upwardmovement of the end of the arm l5. Such pin is mounted in a verticallyadjustable holder 6|.

Upon moving the arm 63 so as to engage the bolt 55 in the dial holemarked Off an arm 62 which is rigid with shaft 52 is brought into aposition directly below the pin 25 and locked against movement. The pin25 is therefore unable to descend and consequently the contact 21 isheld in an elevated position and the motor circuit cannot be closed. 15,As the compressor operates, the pressure is lowered in the evaporatorand consequently in bel-' lows l I. when the pressure decreases to avalue corresponding to the low limit of temperature,

the downward pressure on arm l5 overcomes the spring pressed roller 34and the switch is snapped open.

The lower limit or range of working temperature may be varied by meansof the adjustable coil spring 62'. The ends of this spring abutrespectively against the base In and lock nut 63. Inasmuch as thisspring tends to move the switch arm l6 upward, a movement of the locknut downward increases the upward urge of the spring and makes it moredifficult for the bellows to pull the switch arm down to open the motorcircuit. The compressor therefore operates to produce a lower pressureon the low pressure side of the system. and a correspondingly lowertemperature in the refrigerated region before the motor circuit can beopened.

All of the switch control mechanism of Figs. 2 and 3 described up tothis point is well known and in use and has been set forth in order toshow how my invention may be applied as an attachment thereto, so thatthe advantages thereof may be obtained without the necessity ofsubstituting therefor a different switch.

In applying my invention to the foregoing type of apparatus. I prefer tobring about a defrosting operation periodically and automatically bymeans of a cycle counting mechanism and means which at the end of anydesired number of cycles, by cooperating therewith will alter a normalcycle by increasii {the resistance of the switch arm I5 50 to upwardmotion, so that the motor circuit cannot be closed until the pressure ofthe refrigerant vapor is sufficiently high to produce a defrostintemperature, for example 36 F. One such cycle is ordinarily sufficientfor this purpose, but if de- 55 sired two or even more cycles may bethus altered, after which the normal mode of operation is automaticallyresumed.

The cycle counting device comprises a toothed wheel 64 carried by asleeve or hub 65 which is 60 rotatable on v the pin 19. A slot 66extends through said hub, and a U shaped spring 61 is mounted on the hubwith one arm in said slot so as to frictionally engage the pin is, andprevent the hub from spinning thereon.

65 Inasmuch as the pin I9 is carried by the switch arm ii, the toothedwheel 64 moves up and down with said arm. There is a pawl 68 pivoted onthe screw 66, the latter being threaded in a plate 10 which is securedto the standard 39 by a screw 70 II. This plate has a stop 12 againstwhich the pawl 68 is normally pressed by a spring 13. One end of saidspring is held in an opening 14 in plate 16, and the other in an openingin the free end of the pawl.

75 As the switch arm l5 descends to open themetor circuit at the end ofeach cycle, the toothed wheel 64 is moved in a counterclockwisedirection the distance from one tooth to the next by reason of theengagement of a tooth with the pawl 68. As the switch arm ascends toclose the motor circuit the wheel rides over the pawl without turning.In case the wheel has 60 teeth, it will make one complete rotation forevery 60 cycles of operation of the refrigerating system, or 60 closingsand openings of the motor switch.

The wheel 64 is provided with a horizontal stud 15 which cooperates witha lever 16 to increase the resistance to upward movement of switch arml5 by which the motor/circuit is closed, whereby the temperature of therefrigerant on the low pressure side of the system must rise to adefrosting temperature for at least one cycle of operation out of thetotal number which correspond to the total number of teeth on the wheel.The lever 16 is bent at one end to form a yoke or U which is journaledon the pin II. The free end of said lever has a depending tooth 11 inposition to be engaged by stud 15 as will be described.

Upward movement of the lever 16 is opposed by the following means. Ahole 16 is formed in the dial plate 51 and support to receive the bolt55 of arm 53 and when so situated the arm 62 is in the position shown inFig. 3. There is a rod 19 which is pivoted at one end on a screwthreaded in a block 8|, and the latter is clamped upon the lever 16 bymeans of a plate 82 and headed screws 83. The block 8| normally restsupon the spider l3 as shown and supports the lever 16. Upon the lowerend of the rod 19 is a roller 84, upward movement of which is preventedby arm 62 when in the position shown.

A U-shaped plate 85 having an upper arm 85* and a lower arm 85 issecured to the lever 16 by headed screws 86 and its upper and lower armsare slidable upon a rod 81 which is pivotally mounted on a pin 86carried by rod 19.

By reason of such slidable connection, the free end of lever 16 iscapable of upward movement with respect to the rod 19 and roller 84.Such movement however is resisted by a coil spring 89, the ends of whichabut respectively against the upper surface of arm 85 and the adjustingnut 90 which is threaded upon the upper end of rod 81. The degree ofsuch resistance may be varied by movement of said nut to vary thecompression of said spring.

Whenever the bolt 55 and arm 62 of the control arm 53 are in theposition shown, a defrosting cycle will be automatically and regularlyinterposed within a series of normal or non-defrosting cycles ofoperation of the refrigerating system, as follows:

The succession of normal cycles causes a step by step movement of thetoothed wheel 64 until the stud I5 is brought immediately below thepoint or end of the tooth H of lever 16. At the next upward movement ofthe switch arm l5 brought about by the bellows II for the purpose ofclosing the motor switch to start the motor and drive the compressor,the toothed wheel is carried upward by the pin IS on which it is mountedand the stud 15 engages the end of the tooth 11 and elevates the freeend of the lever 16. The free end of rod 19 however, cannot rise onaccount of the arm 62 being in the path of the roller 84. Consequentlythe plate 85 must slide upon the rod 81 against the resistance of thespring 89. Such resistance is additional or supplementary to theresistance of the spring 46 which also opposes the upward movement ofswitch arm l5, and the effect of such added resistance is to keep themotor circuit open until the refrigerated region attains a temperaturesumciently higher than the normal upper range or limit to causedefrosting of the cooling pipes, for example 36 F.

When such temperature is reached the pressure of the vapor in thebellows H is sumclent to raise the switch arm and close the motorcircuit. The motor thereupon starts and drives the compressor until thetemperature is brought down to the normal lower limit, whereupon thecontraction of the bellows causes a downward movement of the switch armI! and toothed wheel 64. Such movement causes engagement of a tooththereof with the pawl 68 and advances the wheel the pitch distancethereof which brings the stud 15 from under the tooth l1 and restoresthe sequence of normal cycles until the toothed wheel has made anotherrevolution.

By moving arm 53 so that bolt 55 enters a hole other than that shown,for example, to ob tain a lower upper temperature limit, arm 62 is movedaway from contactive relation with roller 84 and the defrostingmechanism is rendered ineffective.

Obviously the proportion of defrosting cycles to normal cycles may bevaried in different ways as, for instance, by varying the number ofteeth upon the wheel 64, or by adding one or more additional studs I5thereto, as indicated at I5, Fig. 3, or by increasing the width of thetooth 11 or of the shank of stud 15 so that more than one downwardmovement of the wheel will be necessary in order to eifect a clearanceof the stud with respect to the tooth.

While I have illustrated my invention in one of its preferred forms asan attachment to the control switch of a well known householdrefrigerating system, the invention is not limited thereto and may beapplied in many different ways to a cyclic refrigerating system of thetype described.

I claim:

1. In a refrigerating system, the combination of a compressor forcompressing a gas or vapor, electrical means comprising an electriccircuit for actuating said compressor, means responsive to a normal lowtemperature limit for opening said circuit, means responsive to a normalhigh temperature limit for closing said circuit, separate resilientmeans opposing the action of said last named means to cause it torespond to a higher closing temperature, and means for automaticallybringing said opposing means into and out of action.

2. In a refrigerating system, the combination of a compressor forcompressing a gas or vapor, an electric motor for driving the compressorand a power circuit for actuating the motor, means including a firstspring responsive to the normal upper temperature limit of therefrigerated region for closing said circuit and means including asecond spring for automatically and temporarily causing said means torespond only to a higher temperature to effect a defrosting operation.

3. An attachment for the electric circuit closing switch of a cyclicrefrigerating system, said switch comprising a pivotal switch arm and afirst spring for causing the closing and opening of the circuit, saidattachment comprising a toothed wheel to be mounted on said switch arm,a pawl for engagement with the teeth of said wheel for imparting a stepby step movement thereto, and means cooperating with said wheelcomprising a separate pivoted arm and a second spring for periodicallyincreasing the resistance of said switch arm to movement for closing thecircuit.

41111 attachment for the electric circuit closing switch of a cyclicrefrigerating system, which switch comprises a pivotal switch arm forcausing the closing and opening of the circuit, said attachmentcomprising means for counting the movements of said switch arm, andmeans including a second pivoted arm and a spring for periodicallyincreasing the resistance of said switch arm to movement for closing thecircuit.

5. Control mechanism for a refrigerating system comprising a flexiblepressure-responsive member, an electric switch, means actuated by saidflexible member for closing and opening said switch, resistance meansexerting force in opposition to pressure exerted against said flexiblemember, separate resistance means adapted to exert an additional forceagainst said flexible member, and means controlled by movement of saidflexible member operating to cause said additional force-exerting meansto act periodically between a plurality of cycles of closing and openingof said switch.

6. Control mechanism for a refrigerating system comprising a flexiblepressure-responsive member, an electric switch, means actuated by saidflexible member for closing and opening said switch, resistance meansexerting force in opposition to pressure exerted against said flexiblemember, separate resistance means adapted to exert an additional forceagainst said flexible member, and means controlled by movement of saidflexible member operating to cause said additional force-exerting meansto act periodically between a plurality of numbered cycles of closingand opening of said switch, said resistance means being separatelyadjustable.

7. Control mechanism for a refrigerating system comprising a flexiblepressure-responsive member, an electric switch, means actuated by saidflexible member for closing and opening said switch, a normally actingspring exerting force in opposition to pressure exerted against saidflexible member, a second spring adapted to exert an additional forceagainst said flexible member, and means controlled by movement of saidflexible member operating to cause said second spring to actperiodically between a plurality of cycles of closing and opening ofsaid switch 8. Control mechanism for a refrigerating system comprising aflexible pressure-responsive member, an energy supply control member,means actuated by said flexible member for actuating said controlmember, resistance means exerting force in opposition to pressureexerted against said flexible member, separate resistance means adaptedto exert an additional force against said flexible member, and meanscontrolled by movement of said flexible member operating to cause saidadditional force-exerting means to act automatically at intervals.

9. Control mechanism for a refrigerating system comprising a flexiblepressure-responsive member, an energy supply control member, meansactuated by said flexible member for actuating said control member,resistance means exerting force in opposition to pressure exertedagainst said flexible member, separate resistance means adapted to exertan additional force against said flexible member, and means controlledby movement of said flexible member operating to cause said additionalforce-exerting means to automatically act periodically between a.numbered plurality of cycles of actuation of said control member.

10. Control mechanism for a refrigerating system comprising a flexiblepressure-responsive member an energy supply control member, meansactuated by said flexible member for actuating said control member, anormally acting spring exerting force in opposition to pressure exertedagainst said flexible member, a second spring adapted to exert anadditional force against said flexible member, means controlled bymovement of said flexible member operating to' cause said second springto act automatically at predetermined intervals and means for separatelyadjusting the force of said springs.

11. Control mechanism for a refrigerating system comprising a flexiblepressure-responsive member, an electric switch, means actuated by saidflexible member for closing and opening said switch, resistance meansexerting force in opposition to pressure exerted against said flexiblemember, separate resistance means adapted to exert an additional forceagainst said flexible member, and pawl and ratchet mechanism controlledby movement of said flexible member operating to cause said additionalforce-exerting means to act periodically between a plurality of cyclesof closing and opening of said switch.

12. A refrigerating system comprising means to supply energy thereto,means for controlling the supply of energy, and means for controllingthe last-mentioned means comprising a normally operative memberresponsive to variations in temperature below an upper limit oftemperature, defrosting mechanism movable to periodically restrain theenergy supply and to restore the supply of energy in response totemperature above said upper limit of temperaturerand manually operablemeans to cause said normally operative member to be responsive to alower upper limit of temperature and to simultaneously render thedefrosting mechanism ineffective.

13. A refrigerating system comprising means to supply energy thereto,means for controlling the supply of energy, and means for controllingthe last-mentioned means comprising a normally operative memberresponsive to variations in temperature below an upper limit oftemperature and spring means acting against said member, defrostingmechanism movable to periodically increase the spring resistance on saidmember to restrain the energy supply and to restore the supply of energyin response to temperature above said upper limit of temperature, andmanually operable means for decreasing the spring resistance on saidnormally operative member to cause said member to be responsive to alower upper limit of temperature and for simultaneously rendering thedefrosting mechanism ineffective.

14. A refrigerating system comprising means to supply energy thereto,means for controlling the supply of energy, and means for controllingthe last-mentioned means comprising a normally operative memberresponsive to variations in temperature below an upper limit oftemperature, defrosting mechanism movable to periodically restrain theenergy supply and to restore the supply of energy in response totemperature above said upper limit of temperature, manually operablemeans to cause said normally operative member to be responsive to alower upper limit of 15. A refrigerating system comprising means 7 tosupply energy thereto, means for controlling the supply of energy, andmeans for controlling the last-mentioned means comprising a normallyoperative member responsive to variations in temperature below an upperlimit of temperature, defrosting mechanism movable step-by-step toperiodically restrain the energy supply and to restore the supply ofenergy in response to temperature above said upper limit of temperature,and manually operable means to cause said normally operative member tobe responsive to a lower upper limit of temperature and tosimultancously render the defrosting mechanism ineffective.

16. Control mechanism for a. refrigerating system including flexiblepressure-responsive means, energy supply control means, means actuatedby said flexible means for actuating said control means, resistancemeans exerting force in opposition to pressure exerted against saidflexible means, separate resistance means adapted to exert an additionalforce against said flexible means, and means to cause said additionalforce-exerting means to act automatically at predetermined intervals.

1'7. Control mechanism for a refrigerating system including flexiblepressure-responsive means, energy supply control means, means actuatedby said flexible means for actuating said control means, resistancemeans exerting force in opposi-- tion to pressure exerted against saidflexible means, separate resistance means adapted to exert an additionalforce against said flexible means and means to cause said additionalforce-exerting means to act periodically, said resistance means beingseparately adjustable.

18. A refrigerating system comprising means to supply energy thereto,means for controlling the supply of energy, and means for controllingthe last-mentioned means comprising a normally operative memberresponsive to variations in temperature below an upper limit oftemperature, defrosting mechanism automatically movable to periodicallyrestrain the energy supply and to automatically restore the supply ofenergy, and manually operable means to cause said normally operativemember to be responsive to a lower upper limit of temperature and tosimultaneously render the defrosting mechanism ineffective.

19. A refrigerating system comprising means to supply energy thereto,means for controlling the supply of energy, and means for controllingthe last-mentioned means comprising a normally operative memberresponsive to variations in l temperature below an upper limit oftemperature and spring means acting against said member, defrostingmechanism automatically movable to periodically increase the springresistance on said member to restrain the energy supply and toautomatically restore the supply of energy, and manually operable meansfor decreasing the spring resistance on said normally operative memberto cause said member to be responsive to a lower upper limit oftemperature and for simultaneously rendering the defrosting mechanismineffective.

20. A refrigerating system comprising means to supply ener'gy thereto,means for controlling the supply of energy, and means for controllingthe last-mentioned means comprising a normally operative memberresponsive to variations in temperature below an upper limit oftemperature, defrosting mechanism automatically movable step by step bysaid control means to a position to periodically restrain the energysupply and to automatically restore the supply of energy, normallyoperative means to cause said normallyoperative member to be responsiveto a lower upper limit of temperature, and means independent of thepresence or absence of frost for preventing the operation of saiddefrosting mechanism to operate as a defrosting means when in itsdefrosting position.

21. A refrigerating system comprising means to supply energy thereto,means for controlling the supply of energy, and means for controllingthe last-mentioned means comprising a normally operative memberresponsive to variations in temperature below an upper limit oftemperature, defrosting mechanism automatically movable step-by-step toperiodically restrain the energy supply and to automatically restore thesupply of energy, and manually operable means to cause said normallyoperative member to be responsive to a lower upper limit of temperatureand to simultaneously render, the defrosting mechanism ineffective.

22. A refrigerating system comprising means to supply energy thereto,means for controlling the supply of energy, and means for controllingthe last-mentioned means comprising a normally operative memberresponsive to variations in temperature below a given temperature,defrosting mechanism movable by one of said control means toperiodically restrain the energy supply and to restore the supply ofenergy, and means independent of the presence or absence of frost forpreventing the operation of said defrosting mechanism.

23. Control mechanism for a refrigerating system including normallyactive resilient mechanism responsive to variations in temperature of anobject to be cooled and movable to vary supply of energy to maintain apredetermined condition of efrigeration, normally inactive resilientmechanism, means to intermittently and automatically activate thesecond-mentioned mechanism to take over control oiiv energy supply so asto cause defrosting, means to automatically restore the second-mentionedmechanism to inactive condition, and means to simultaneously adjust thefirstmentioned mechanism to different temperature and render thesecond-mentioned mechanism ineffective.

24. In a refrigerating system, a cooling element, a first means normallycontrolling the operation of the system to maintain the temperature ofthe cooling element at a predetermined normal value, a second means formodifying operation of the system to allow the temperature of saidcooling element to rise above said normal value, and an automaticintermittent actuator operated by said first means for instigatingoperation of said second means, said second means being automaticallyrendered ineffective to so modify the operation upon a predetermineddrop in temperature of said cooling element below normal value.

.25. Refrigerating apparatus comprising an evaporator, means forcirculating a refrigerating medium through the evaporator, means forcontrolling the operation of the refrigerating apparatus to maintain thetemperature of the evaporator substantially constant, said control meansincluding adjusting means to obtain a different temperature in saidevaporator, automatic means for defrosting said evaporator, and meansoperated by said control means for preventing the operation of saiddefrosting means.

26. Refrigerating apparatus comprising an evaporator, means forcirculating a refrigerating medium through the evaporator, means forcontrolling the operation of the refrigerating apparatus to maintain thetemperature of the evaporator substantially constant, means foradjusting said control means to obtain a lower temperature in saidevaporator, automatic means for defrosting said evaporator, and meansoperated by said adjusting means for preventing the operation of saiddefrosting means.

27. Refrigerating apparatus comprising an evaporator, means forcirculating a refrigerating medium through the evaporator, means forcontrolling the operation of the refrigerating apparatus to maintain thetemperature of the evaporator said . substantially constant, means foradjusting said control means to a plurality of selective positions toobtain a plurality of different temperatures in said evaporator,automatic means for defrosting said evaporator, and means operated bythe movement of said adjusting means to at least one of the selectivepositions to prevent the operation of said defrosting means.

28. Refrigerating apparatus comprising an evaporator, means forcirculating a refrigerating medium through the evaporator, a switch forcontrolling the operation of the refrigerating apparatus to maintain thetemperature of the evaporator substantially constant, said switch beingprovided with a plurality of selective adjustable positions to maintainthe temperature of the evaporator at the selected temperatures,automatic means for defrosting the evaporator, and means operated by themovement of the switch to at least one of the selected positions toprevent the operation of said defrosting means.

29. A refrigerating system comprising means to supply energy thereto,means for controlling the supply of energy, and means for controllingthe last-mentioned means comprising a normally operative memberresponsive to variations in temperature below a given temperature,defrosting mechanism, and means independent of the presence or absenceof frost for operating said defrosting mechanism to periodicallyrestrain the energy supply and to restore the supply of energy inresponse to temperature above said given temperature, and means torender said defrosting mechanism ineffective.

EDWIN R. GILL, SR.

